| Summary: | 碩士 === 中原大學 === 化學工程學系 === 85 ===
In Newtonian fluid, steady-streaming flow, a nonlinear phenomenon, is originated from convective acceleration. However, in non-Newtonian fluid, due to the dependence of viscoelasticity on shear rate, the viscoelastic effect could also be a source of steady-streaming. In this study, the steady-streaming flow in non-Newtonian fluid was investigated in rigid and elastic tubes by the photochromic method, a flow visualization technique.
It was observed that steady-streaming could be generated when non-Newtonian fluid flowed oscillatingly through a circular rigid pipe. The steady-streaming had a pattern that the fluid drifted upstream near the wall and downstream in the core. It was also found that this nonlinear flow phenomenon was induced by the elasticity of the non-Newtonian fluid. In addition, the steady-streaming velocity increased with increasing oscillating flow rate, decreasing frequency and increasing fluid elasticity.
In elastic tube, for dilute Xanthan-gum/water solution (<0.04wt%) ,the steady-streaming pattern was similar to that of non-Newtonian fluid. Nevertheless, when the concentration increased to 0.3wt%, the flow pattern changed drastically. It was also observed, for 0.3wt% Xanthan-gum solution, the steady streaming velocity increased with increasing oscillating flow rate, but decreased first and the increased with increasing frequency.
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